Reference level adjustment for calibration of dual-gate transistors

ABSTRACT

Disclosed are various embodiments related to dual-gate transistors and associated calibration circuitry. In one embodiment, dual-gate transistors may be configured in a sense amplifier arrangement, and calibration circuitry can be used to adjust an input offset of the sense amplifier. In another embodiment, a reference level voltage utilized in an amplifier with dual-gate transistors can be adjusted during a calibration sequence, and may be substantially unchanged from its nominal value outside of the calibration sequence. In another embodiment, a calibration sequence can be utilized to determine circuit results from a circuit including dual-gate transistors, and to adjust control gates to more closely coincide with expected or desired results. In yet another embodiment, a semiconductor memory device can include a memory array with amplifiers that include dual-gate transistors, as well as associated calibration circuitry.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 62/126,954, filed on Mar. 2, 2015, which is herebyincorporated by reference as if set forth in full in this applicationfor all purposes.

FIELD OF THE INVENTION

The present invention generally relates to the field of semiconductordevices, and more particularly, to dual-gate transistors and associatedcalibration circuitry.

BACKGROUND

A multi-late device or multiple gate field-effect transistor (MuGFET)may be a metal oxide semiconductor field-effect transistor (MOSFET) thatincorporates more than one gate into a single device. Examples ofmultigate devices include FinFETs. Flexfets, tri-gate transistors, andgate-all-around (GAA) FETs. The multiple gates ma be independentlycontrolled, or may electrically act as a single gate in some cases. Forindependently controlled dual gate transistors, one gate may beconsidered a control gate and the other gate may be considered a signalgate, whereby a voltage on the control gate can affect the thresholdvoltage of the transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing an example amplifier andcalibration control arrangement, in accordance with embodiments of thepresent invention.

FIG. 2 is a schematic block diagram showing an example amplifier circuitwith dual-gate transistors, in accordance with embodiments of thepresent invention.

FIG. 3 is a schematic block diagram showing an example calibrationcontroller, in accordance with embodiments of the present invention.

FIG. 4 is a schematic block diagram showing an example calibrationtiming control circuit, in accordance with embodiments of the presentinvention.

FIG. 5 is a schematic block diagram showing an example calibrationcontrol circuit, in accordance with embodiments of the presentinvention.

FIG. 6 is a waveform diagram showing an example calibration controloperation, in accordance with embodiments of the present invention.

FIG. 7 is a schematic block diagram showing an example reference leveladjustor, in accordance with embodiments of the present invention.

FIG. 8 is a schematic block diagram showing an example adjustmentvoltage generator, in accordance with embodiments of the presentinvention.

FIG. 9 is a flow diagram showing an example method of controllingdual-gate transistors, in accordance with embodiments of the presentinvention.

FIG. 10 is a schematic block diagram showing an example calibrationcontrol arrangement for a memory array, in accordance with embodimentsof the present invention.

FIG. 11 is a schematic block diagram showing an example of register andmultiplexer circuitry for calibration control for a memory array, inaccordance with embodiments of the present invention.

FIG. 12 is a schematic block diagram showing an example amplifier andcalibration control arrangement for an input receiver, in accordancewith embodiments of the present invention.

FIG. 13 is a schematic block diagram showing an example input receiverwith dual-gate transistors, in accordance with embodiments of thepresent invention.

FIG. 14 is a schematic block diagram showing an example calibrationcontroller for an input receiver, in accordance with embodiments of thepresent invention.

FIG. 15 is a schematic block diagram showing an example amplifier andcalibration control arrangement for an input receiver with differentialinputs, in accordance with embodiments of the present invention.

FIG. 16 is a schematic block diagram showing an example input receiverwith dual-gate transistors and differential inputs, in accordance withembodiments of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

Reference will now be made in detail to particular embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction withparticular embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be readilyapparent to one skilled in the art that the present invention may bepracticed without these specific details. In other instances, well-knownmethods, procedures, components, etc. have not been described in detailso as not to unnecessarily obscure aspects of the present invention.

Some portions of the detailed descriptions which follow are presented interms of processes, procedures, block arrangements, logic blocks,functional blocks, processing, circuit schematics, and/or other symbolicrepresentations of operations or device arrangements. These descriptionsand representations are generally used by those skilled in the relevantarts to effectively convey the substance of their work to others skilledin the art.

Particular embodiments can advantageously provide circuits, methods, andstructures, to facilitate circuit operation, or to otherwise modifycircuit operation, for circuits including multigate (e.g., FinFET)devices. For example, particular embodiments can advantageously provideapproaches that allow for calibration or adjustment of operation fordual-gate transistors, such as in a sense amplifier or input receiverconfiguration. Various embodiments relate to any type of transistorhaving at least one control gate and at least one signal gate, whereby avoltage on the control gate can be used to affect a threshold voltage ofthe transistor. For example, an increased control gate voltage for anNMOS FinFET can reduce the transistor threshold voltage, while adecreased control gate voltage for a PMOS FinFET can reduce thatthreshold voltage.

In one embodiment, dual-gate transistors may be configured in a senseamplifier arrangement, and calibration circuitry can be used to adjustan input offset of the sense amplifier. In another embodiment, areference level voltage utilized in an amplifier with dual-gatetransistors can be adjusted during a calibration sequence, and may besubstantially unchanged from its nominal value outside of thecalibration sequence. In another embodiment, a calibration sequence canbe utilized to determine circuit results from a circuit includingdual-gate transistors, and to adjust control gates to more closelycoincide with expected or desired results. In yet another embodiment, asemiconductor memory device can include a memory array with amplifiersthat include dual-gate transistors, as well as associated calibrationcircuitry. These and various other embodiments will be discussed in moredetail below.

Particular embodiments are suited to chips or devices that includemultigate, such as dual-gate (e.g., FinFET), transistors arranged incircuitry whereby matching (or mismatching) of various circuitattributes can result in different circuit behavior. For example, inputoffset and transistor behavior matching problems, particularly at lowervoltages and with increasingly smaller device geometries, can causeinconsistent or incorrect circuit operation. In particular embodiments,such matching problems can be addressed by “calibration” circuitrywhereby the circuit can be tested from each “side” or expected outputstate, in order to determine a calibration result that can mitigatepotential matching problems. In some cases, a deliberate skew can beintroduced into a circuit in order to favor one result or expectedoutput over another. Further, the calibration result can be effectivelyapplied to control gates, such as those of dual-gate transistors in thecircuitry utilizing matching or otherwise coupled devices. In this way,multigate transistor based circuitry may be suitable for high-volumemanufacturing in advanced process techniques, and also can accommodatelower operating voltages.

Of course, while dual-gate FinFET devices are primarily used in theexamples herein, any suitable multigate transistor or device can beemployed. In particular, any type of transistor whereby a thresholdvoltage can be controlled or adjusted by one of the transistor gates(e.g., a control gate) can be utilized. In addition, while differentialand sense amplifiers are exemplified herein, any type of amplifying ormatching (e.g., current mirror) circuitry can be employed in certainembodiments. Further, as used herein “calibration” can refer to anadjustment or potential adjustment resulting from calibration circuitsthat aim to improve or to otherwise adjust a particular characteristicor likely output of a circuit having matched or otherwise relatedmultigate devices. In addition, a “calibration sequence” can refer to aseries of cycles (e.g., as defined by a clock), including “phases” orportions of the calibration sequence, in which calibration settings aredetermined. Also, “side” as used herein may indicate that thecalibration is done by considering each side, or way the circuit havingmatched multigate devices may operate, such as each expected outputstate (e.g., an amplifier that outputs a logic 1 or a logic 0 based onthe amplifier inputs).

In particular embodiments, dual-gate transistors may be configured in asense amplifier arrangement, and calibration circuitry can be used toadjust an input offset of the sense amplifier. In one embodiment, asemiconductor device can include: (i) a first dual-gate transistorhaving a signal gate coupled to a first data input, and a control gatecoupled to a first control signal; (ii) a second dual-gate transistorhaving a signal gate coupled to a second data input, and a control gatecoupled to a second control signal, where the first and second dual-gatetransistors are arranged in an amplifier configuration; and (iii) acalibration circuit configured to adjust the first and second controlsignals when enabled, and to maintain the first and second controlsignals when disabled.

Referring now to FIG. 1, shown is a schematic block diagram of anexample amplifier and calibration control arrangement, in accordancewith embodiments of the present invention. In example 100, senseamplifier 102 can receive data input (DI), such as from a memory array(e.g., DRAM, SRAM, etc.). Offset calibration control 104 can receive acalibration enable command signal (CENCMD), a clock signal (CLK), areference voltage level (REF), and adjustment setting signals(ADJSET[7:0]), as well as data output (DO) from sense amplifier 102.Offset calibration control 104 can provide control gate signals (CGR,CGD) and an adjusted reference level (REFADJ) to sense amplifier 102. Inaddition, a non-calibration sense amplifier enable signal (SENNCB) canbe input to NAND-gate 106 along with calibration sequence senseamplifier enable signal (SENCB), such that a sense amplifier enablesignal (SEN) can be output from NAND-gate 106. Thus, sense amplifier 102can be enabled either for normal (e.g., memory cell data reading)operations, or for a calibration operation as described herein.

Referring now to FIG. 2, shown is a schematic block diagram of anexample amplifier circuit 102 with dual-gate transistors, in accordancewith embodiments of the present invention. For example, transistors 202and 204 can be FinFETs with independent control and signal gates.Dual-gate PMOS transistor 202 can receive the data input at a signalgate thereof, and control signal CGD can connect to a control gatethereof. Also, dual-gate PMOS transistor 204 in a matching configurationin this case can receive adjusted reference level REFADJ at a signalgate thereof, and control signal CGR can connect to a control gatethereof. Cross-coupled inverter structures including PMOS transistors206 and 208 and NMOS transistors 210 and 212 can form a sense amplifierarrangement.

Sense amplifier 102 can be enabled based on sense amplifier enablesignal SEN, which can be inverted via inverter 220 to form an active lowenable signal SENB. Active low enable signal SENB can connect to gatesof PMOS transistor 214, NMOS transistor 216, and NMOS transistor 218.Thus, when sense amplifier enable signal SEN is high, either due to anenabled calibration sequence or when in normal operation during anon-calibration sequence, sense amplifier 102 can sense and amplify adifference on data input DI as compared to adjusted reference levelREFADJ. As will be discussed in more detail below, adjusted referencelevel REFADJ can be the same, or substantially the same as, a normal ora nominal reference level REF when not in a calibration mode.

As described herein, data input DI can be held low (e.g., at ground or0V) during a calibration sequence, and adjusted reference level REFADJcan be increased (e.g., by VADJ during a phase 1 of the calibrationsequence) and then decreased (e.g., by VADJ during a phase 2 of thecalibration sequence). Thus, adjusted reference level REFADJ can becontrolled to be greater than or less than the corresponding data input,such as by a value of VADJ. However, data input DI, while being held ata low level in many of the examples described herein, may also be anyother voltage level, such as an intermediate (e.g., half of the supplyvoltage) voltage level. In such a case, that intermediate level can beconsidered as a nominal reference level, and adjusted reference levelREFADJ can be controlled to be greater than or less than that nominalreference level.

In this way, particular embodiments can accommodate any suitable arraystructure by controlling the adjusted reference level with respect to anominal reference level. Further, the low level on data input DI may bea suitable level if corresponds to a default storage level in associatedmemory cells or other data being amplified. That is, the calibrationsequence may be applied as part of a power up or initializationoperation whereby the default levels to be amplified can be considered,and the adjusted reference level can be adjusted with respect to thosedefault levels as represented by data input DI. By accommodating thedefault data state associated with data input DI, the calibrationsequence can be simplified because actual access of the memory cell orassociated circuitry may not be necessary.

However, in other cases, and may be desirable to access the memory cellor associated circuitry, and to use that state as part of thecalibration process. For example, in such an approach the adjustedreference level REFADJ may be substantially fixed, but based on the datapattern employed and accessed via data input DI, the calibrationsequence as described herein can still be carried out. Thus, either oneof the signal gates for dual-gate transistors 202 and 204 can besubstantially fixed, while the other is adjusted (e.g., by increasing ordecreasing by an adjustment voltage) in order to carry out thecalibration sequence. In any event, particular embodiments are suitableto a wide variety of memory array, circuitry, and associated datastructures by way of data input and adjusted reference levelmanipulation during a calibration sequence.

The sense amplifier output signal can be developed on the nodes that areinput to inverters 222 and 224, thus producing sense amplifier outputsignals as SOB and SO, respectively. In this particular example, signalscan then be input to the SR flip-flop formed by NAND-gates 226 and 228.The output of the SR flip-flop can be provided to buffers 230 and 232 togenerate data output DO. In other cases, the SR flip-flop structure maynot be utilized, and data direct from sense amplifier output signal SOcan be buffered to provide data output DO. In certain embodiments, acalibration sequence can be employed to determine settings on controlsignals CGD and CGR in order to provide better matching characteristics,such as substantially negated input offset effects on operation of senseamplifier 102.

In certain embodiments, the calibration sequence can be employed todetermine settings on control signals CGD and CGR in order to modifycircuit operation, such as by providing an intentional skew to favor oneside or the other. Thus, the calibration sequence need not be usedmerely to improve aspects of circuit operation, such as reduction ofinput offset. Rather, any circuit characteristic, and particularly thoseaffected by threshold voltage modification via a control gate of adual-gate transistor, can be modified via the calibration sequence.Further, while a specific sense amplifier arrangement and associatedcircuit is shown in this particular example, certain embodiments canaccommodate any suitable type of amplifier or circuit structure thatincludes dual-gate transistors. Further, transistors other than 202 and204 may also be dual-gate transistors consistent with a particularprocess technology. For example, all transistors may be formed in aFinFET process technology, and transistors other than 202 and 204 may beoperated such that their control and signal gates are connectedtogether.

Referring now to FIG. 3, shown is a schematic block diagram of anexample calibration controller, in accordance with embodiments of thepresent invention. Offset calibration control 104 can includecalibration timing control 302, calibration control circuit 304, andreference level adjuster 306. Calibration timing control 302 cangenerate various timing signals utilised by other circuits in thecalibration sequence or process. For example, calibration timing control302 can receive calibration enable command signal CENCMD and clocksignal CLK, and may generate a calibration enable signal (CEN), acalibration enable for “phase 1” of the calibration sequence signal(CENP1), a calibration enable for “phase 2” of the calibration sequencesignal (CENP2), an enable latch control signal for phase 1 (ELP1), anenable latch control signal for phase 2 (ELP2), an update control gatesignal pulse (UDCGS), and calibration sequence sense amplifier enablesignal SENCB.

Calibration control circuit 304 can receive calibration enable signalCEN, phase 1 enable latch control signal ELP1, phase 2 enable latchcontrol signal ELP2, update control gate signal pulse UDCGS, and dataoutput signal DO from sense amplifier 102, and may generate controlsignals CGR and CGD for the control gates of transistors 202 and 204 insense amplifier 102. Reference level adjuster 306 can receive referencelevel REF, adjustment setting signals ADJSET[7:0], calibration enablesignal CEN, phase 1 calibration enable signal CENP1, and phase 2calibration enable signal CENP2, and may generate adjusted referencelevel REFADJ.

Adjustment setting signals ADJSET[7:0] can be any inputs used foradjusting the reference level, and may be dynamically input via addresspins or other signals that are coupled to external chip circuitry. Insome cases, the adjustment setting signals can be modified from onecalibration sequence to the next, such as when corresponding to oneportion of a memory array versus another, or one type of circuitryversus another. As will be discussed in more detail below, phasecalibration enable signals CENP1 and CENP2 can be used to control whenadjusted reference level REFADJ is an increased or decreased voltagerelative to reference level, in order to effectively test both sides ofsense amplifier 102.

Referring now to FIG. 4, shown is a schematic block diagram of anexample calibration timing control circuit, in accordance withembodiments of the present invention. Calibration timing control circuit302 can include counter 402, which can generate count signals CT0, CT1,and CT2 when enabled, and may be based on rising edges of the clocksignal. For example, the count signals can count 8 cycles for eachcalibration sequence activation that is initiated via the CENCMD signal,as input to D-type flip-flop 404. Thus, a detected activation of CENCMDby DFF 404 can be used as the set input to SR flip-flop 410, the outputof which can be buffered by inverters 412 and 414 to generatecalibration enable signal CEN.

Calibration enable signal CEN can remain high for substantial portionsof the calibration sequence. The reset of SR flip-flop 410, and thuscalibration enable signal CEN, can occur when the count signal bits areall one, as determined by NAND-gate 406 and inverter 408. Thus, CEN canbe activated upon an initial count cycle, and the activated upon a lastcount cycle, as shown in the example waveforms of FIG. 6. Of course,counters other than 3-bit counters can be employed as necessary for agiven application. In some cases, the calibration sequence may take moreclock cycles or fewer clock cycles, depending on the amplifiercharacteristics and a clock frequency, among other factors. In thesecases, different types of counters 402 can be employed.

The update control signal UDCGS for the control gates of dual-gatetransistors 202 and 204 can be generated as a one-shot or pulse signalupon a falling edge of calibration enable CEN. This pulse signal can bea duration substantially of delay circuit 416, an output of which can beinverted via inverter 418, and input to NOR-gate 420. NOR-gate 420 canthus provide a high going pulse signal upon a high to low transition ofcalibration enable signal CEN. In this way, the control signalsconnected to the control gates of dual-gate transistors 202 and 204 mayonly be updated upon the substantial completion of the calibrationsequence. Also, these control signals CGR and CGD may be held low duringthe calibration enable signal activation time, and then allowed toupdate upon deactivation or completion of the calibration sequence. Inother cases, the control signals CGR and CGD may be held to a differentstate (e.g., high) during the calibration sequence. In either case, theupdated states of control signals CGR and CGD can occur upon completionof the calibration sequence.

The calibration sequence may generally be divided into 2 phases, eachphase corresponding to testing of one side of the amplifier, or othermatched circuit under consideration. Again referring to FIG. 4 inconjunction with FIG. 6, phase 1 calibration enable signal CENP1 can beactivated via SR flip-flop 434 when the count signals are CT[2:0]=000 asdetected by NOR-gate 428 and when calibration enable signal CEN is high,as determined via NAND-gate 430 and inverter 432. Phase 1 calibrationenable signal CENP1 can be deactivated when CT[2:0]=011 and calibrationenable CEN is high, as determined via inverter 422, NAND-gate 424, andinverter 426 having an output connected to the reset terminal of SRflip-flop 434. Phase 2 calibration enable signal CENP2 can be activatedvia SR flip-flop 440 when the count signals are CT[2:0]=100 as detectedby inverter 442 and NOR-gate 444 and when calibration enable signal CENis high, as determined via NAND-gate 446 and inverter 448. Phase 2calibration enable signal CENP2 can be deactivated when CT[2:0]=111 andcalibration enable CEN is high, as determined via NAND-gate 436, andinverter 438 having an output connected to the reset terminal of SRflip-flop 440.

Sense amplifier enable for calibration signal SENCB can be an active lowsignal, which can be activated when CT[1:0]=01 by way of inverter 450and NOR-gate 452. The output of NOR-gate 452 can connect to the resetterminal of SR flip-flop 456 for activating the sense amplifier duringthe calibration sequence. The amplifier can be disabled during thecalibration sequence via NOR-gate 454, which can set SR flip-flop 456 todeactivate SENCB when phase calibration enable signals CENP1 and CENP2are both low. Of course, depending upon how long it takes for suitablesignal development to occur at the amplifier (or other circuit underconsideration) outputs, the timing of enable signal SENCB can bedifferent. For example, the timing of activation of signal SENCB can bemore or less than the 2 clock cycles as shown in FIG. 6.

The enable latch control signals for phase 1 (ELP1) and phase 2 (ELP2)can be activated during a count cycle as CT[1:0]=10, as detected byinverter 462 and NOR-gate 464. These enable latch control signals can beabout a duration of a high level of CLK, which can be input toNAND-gates 458 and 466. The other input of NAND-gates 458 and 466 can bethe output from NOR-gate 464, which may indicate or align with theproper clock cycle in the calibration count sequence based on the countsignals. Phase 1 enable latch control signal ELP1 can be activated whenphase calibration enable signal CENP1 is high, and may be generated viaNOR-gate 460, which also receives an output from NAND-gate 458 and aninverted version of CENP1 via inverter 470. Phase 2 enable latch controlsignal ELP2 can be activated when phase calibration enable signal CENP2is high, and may be generated via NOR-gate 468, which also receives anoutput from NAND-gate 466 and an inverted version of CENP2 via inverter472.

Referring now to FIG. 5, shown is a schematic block diagram of anexample calibration control circuit, in accordance with embodiments ofthe present invention. Calibration control circuit 304 can include latchcircuits 502 (e.g., 502-0, 502-1, 502-2, and 502-3). Phase 1 enablelatch control signal ELP1 can be used to control opening/closing of thetransmission gate in latch circuit 502-0. Thus, when ELP1 is high, NMOStransistor 506-0 can be turned on, and PMOS transistor 504-0 can also beturned on via inverter 514-0, to allow the data output from the senseamplifier to be captured in latch 502-0 as a first phase result. Onceenable latch control signal ELP1 goes low to turn off the transmissiongate, this first phase result can be held via inverters 508-0 and 510-0,and may be buffered via inverter 512-0.

Similarly, phase 2 enable latch control signal ELP2 can be used to openthe transmission gate in latch circuit 502-2. Thus, when ELP2 is high,NMOS transistor 506-2 can be turned on, and PMOS transistor 504-2 canalso be turned on via inverter 514-2, to allow the data output from thesense amplifier to be captured in latch 502-2 as a second phase result.Once enable latch control signal ELP2 goes low to turn off thetransmission gate, this second phase result can be held via inverters508-2 and 510-2, and may be buffered via inverter 512-2. In order tomaintain the states of control signals CGR and CGD until the end of thecalibration sequence, latch circuit 502-1 can be employed to allow thefirst result to pass through only when update control signal UDCGS ispulsed high. Similarly, latch circuit 502-3 can be utilized to allow thesecond result to pass through only when update control signal UDCGS ispulsed high.

During the calibration sequence, as indicated by calibration enablesignal CEN being high, NOR-gates 520 and 516 can be used to keep controlsignals CGR and CGD low. These control signals may be held to a same(e.g., low level) until the calibration sequence is complete.Alternatively, control signal CGR and CGD can be held to another (e.g.high) level during the calibration process. In any event, update controlsignal UDCGS may then pulse high in response to calibration enablesignal CEN going low, and the appropriate post-calibration states canthen be set and maintained on control signals CGR and CGD via NAND-gate518 and NOR-gates 516 and 520.

The particular logic employed as to converting the phase 1 and phase 2calibration test results into updated states on control signals CGR andCGD can vary depending on the types of dual-gate transistors (e.g., NMOSversus PMOS) that are used, as well as the data inputs to the amplifieror other circuit under test for the given phase. In one particularexample, Table 1 below shows example states of the amplifier due tovarious calibration interrogations for the two phases of the calibrationsequence, and resulting considerations for control signals CGR and CGD.

TABLE 1 Calibration CGR CGD Phase DI REFADJ DO ConsiderationsConsiderations 1 0 +VADJ 0 Default Default 1 Increase CGR Hold 2 0 −VADJ0 Hold Increase CGD 1 Default Default

Thus, the “default” considerations may represent cases where theexpected result in reading sense amplifier 102 has occurred. Since thecircuit operated according to expectations, control signals CGR and CGDcould remain the same post calibration sequence. However, control signalCGR and CGD could also be changed such that the margin of theamplification of corresponding data is increased, thereby stillpresenting the expected result for these cases, and possibly improvingor otherwise modifying other results. Also, the “hold” consideration cangenerally be with respect to the corresponding CGR/CGD consideration.Thus, an increase CGR consideration and a hold CGD consideration couldalternatively be presented as a hold CGR consideration and a decreaseCGD consideration. Thus, many possible variations exist as to CGR/CGDconsiderations and possible interpretations in particular embodiments.

In any event, the CGR and CGD considerations found in Table 1 above canthen be converted to control signal CGR and CGD settings to bemaintained after the calibration sequence is complete. Example mappingsof CGR/CGD considerations to associated control signal settings areshown below in Table 2. In this particular example, the default/holdstates may be low level states because CGR and CGD are held low whencalibration enable signal CEN is active. As discussed above, otherinterpretations as well as other values of the default/hold states mayalso be allowed in particular embodiments, as Tables 1 and 2 merelyrepresent one particular set of examples of calibration result andassociated control signal manipulation.

TABLE 2 DO DO Updated Updated Phase 1 Phase 2 CGR CGD Result ResultSettings Settings 0 0 0 1 0 1 0 0 1 0 0 0 1 1 1 0

Referring now to FIG. 6, shown is a waveform diagram of an examplecalibration control operation, in accordance with embodiments of thepresent invention. Waveforms 600 can include calibration enable commandbeing high on a positive edge of CLK in order to activate thecalibration sequence. Count signals CT[2:0] can cycle from 000 to 111 asshown to define the various cycles that are part of the calibrationsequence. In cycle CT[2:0]=000, phase calibration enable signal CENP1can go high, which can also initiate a change in the adjusted referencelevel (REFADJ) to be VADJ (e.g., about 200 mV) greater than the nominalreference level. In cycle CT[2:0]=001, the sense amplifier can beenabled for the calibration sequence by SENCB going low. Thus, signaldevelopment based on a difference between data input DI and the adjustedreference level can begin upon activation of the calibration senseamplifier enable signal.

In cycle CT[2:0]=010, enable latch control signal ELP1 can pulse high inorder to allow for the phase 1 calibration result to be captured. Thus,the time from SENCB going low until ELP1 goes high should be sufficientto allow for suitable signal development on the sense amplifier. Incycle CT[2:0]=011, phase calibration enable signal CENP1 can go low,which can initiate a change in adjusted reference level REFADJ back tothe nominal reference level, as well as disabling of the sense amplifierby SENCB going high. This can complete the first phase of thecalibration sequence. In cycle CT[2:0]=100, the second phase of thecalibration sequence can begin with phase calibration enable signalCENP2 going high, and essentially the process can be completed for theother side of the sense amplifier or other circuitry underconsideration. This can also initiate a change in the adjusted referencelevel (REFADJ) to be VADJ less than the nominal reference level.

In cycle CT[2:0]=101, the sense amplifier can again be enabled for thecalibration sequence by SENCB going low. In cycle CT[2:0]=110, enablelatch control signal ELP2 can pulse high in order to allow for the phase2 calibration result to be captured. Thus, the time from SENCB going lowuntil ELP2 goes high should be sufficient to allow for suitable signaldevelopment on the sense amplifier. While in this case these timings arethe same, depending on the particular circuit under consideration andthe purpose of performing the calibration sequence, the timing betweenSENCB going low until ELP1 versus ELP2 going high may be different. Incycle CT[2:0]=111, phase calibration enable signal CENP2 can go low,which can initiate a change in adjusted reference level REFADJ back tothe nominal reference level, and disabling of the sense amplifier bySENCB going high. This can substantially complete the second phase ofthe calibration sequence. In addition, update control signal UDCGS canpulse high to allow updating of control signals CGR and CGD when thecalibration sequence is completed.

In various embodiments, a reference level utilised in an amplifier withdual-gate transistors can be adjusted during a calibration sequence, andmay be substantially unchanged outside of the calibration sequence. Inone embodiment, a semiconductor device can include: (i) a firsttransmission gate coupled between a reference voltage and an adjustedreference voltage, and being off during a calibration sequence, wherethe calibration sequence comprises first and second phases; (ii) adigital-to-analog converter (DAC) configured to provide an adjustmentvoltage; (iii) second and third transmission gates coupled between thereference voltage and the adjusted reference voltage, and being onduring the first phase and off during the second phase; and (iv) fourthand fifth transmission gates coupled between the reference voltage andthe adjusted reference voltage, and being off during the first phase andon during the second phase.

Referring now to FIG. 7, shown is a schematic block diagram of anexample reference level adjustor, in accordance with embodiments of thepresent invention. Reference level adjustor 306 can include varioustransmission gates that can allow one of a nominal reference level(REF), REF+VADJ, or REF−VADJ, to pass as adjusted reference levelREFADJ, depending on the status of the calibration sequence. Whenneither of phase 1 or phase 2 calibration enable signal is active,transmission gate 704/706 can be turned on via the control of NOR-gate702 and inverter 708. During this time, nominal reference level REF canpass through as adjusted reference level REFADJ, such as during normalor non-calibration operation. In other cases, such as when the datainput as opposed to the reference level is to be altered during thecalibration sequence, or other external controls allow for manipulationof one or both of the signal gate inputs under consideration, thiscircuit may be bypassed.

During phase 1 of the calibration sequence when CENP1 is active,transmission gates 718/720 (with inverter 716 control) and 726/728 (withinverter 724 control) can be turned on to allow VADJ voltage source 722to be added to nominal reference level REF. In this way, the senseamplifier can be tested with an increased input value on the referenceside in order to test the amplifier behavior, such as for possible inputoffset, or other circuit performance aspects. Similarly, during phase 2of the calibration sequence when CENP2 is active, transmission gates712/714 (with inverter 710 control) and 732/734 (with inverter 730control) can be turned on to allow VADJ voltage source 722 to besubtracted from nominal reference level REF. In this way, the senseamplifier can be tested with a decreased input value on the referenceside in order to test the amplifier behavior, such as for possible inputoffset or other circuit performance aspects on the “other” side, or fromanother expected output.

Referring now to FIG. 8, shown is a schematic block diagram of anexample adjustment voltage generator, in accordance with embodiments ofthe present invention. Example adjustment voltage generator 722 caninclude digital to analog converter (DAC) 816, which can set adjustedvoltage value VADJ based on captured adjustment setting inputsADJSET[7:0]. Thus in this particular example, DAC 816 can be an 8-bitDAC. Adjustment settings ADJSET can be captured on a bit by bit basisvia latch circuits 802 (e.g., 802-0, 802-1, 802-2, . . . 802-7). Asdiscussed above, the adjustment settings can be dynamically input to thedevice, and the settings can change at any time outside of thecalibration sequence (e.g., when calibration enable is low). Further,default values can be used for these adjustment settings, and anysuitable external pins mapped to such adjustment setting signalsADJSET[7:0] for changing the values, can be employed.

As shown in latch circuit 802-0, calibration enable signal CEN when lowcan allow the transmission gate to open. Thus, when CEN is low, PMOStransistor 804-0 can be turned on, and NMOS transistor 806-0 can also beturned on via inverter 814-0, to allow ADJSET[0] to be captured in latch802-0. Once calibration enable signal CEN goes high to turn off thetransmission gate, this adjustment setting bit can be held via inverters808-0 and 810-0, and may be buffered via inverter 812-0 to be suppliedto DAC 816. In addition, DAC 816 can be enabled only during CENactivation times (via input EN), in order to save power. Further, anysuitable range of values (e.g., 25 mV, 50 mV, . . . 200 mV, etc.) can besupported via DAC 816. Also, the particular range or choices ofadjustment voltage VADJ can be set (e.g., via the adjustment settingssignals) based on the particular amplifier or circuit underconsideration, as well as based on process and operating voltage, amongother factors.

In certain embodiments, a calibration sequence can be utilised todetermine circuit results from a circuit including dual-gatetransistors, and to adjust control gates to more closely coincide withexpected results. In one embodiment, a method of controlling dual-gatetransistors can include: (i) activating a calibration sequence havingfirst and second phases in response to a calibration command; (ii)during the first phase, increasing a first data input at a signal gateof a first dual-gate transistor by an adjustment voltage, and storing afirst result; (iii) during the second phase, decreasing the first datainput, and storing a second result; and (iv) using the first and secondresults to set first and second control signals, wherein the firstcontrol signal is coupled to a control gate of the first dual-gatetransistor, and the second control signal is coupled to a control gateof the second dual-gate transistor.

Referring now to FIG. 9, shown is a flow diagram of an example method900 of controlling dual-gate transistors, in accordance with embodimentsof the present invention. The flow can begin at 902, and a calibrationsequence can be activated in response to a calibration command at 904.For example, calibration enable command/signal CENCMD can be latched ona rising edge of CLK by D-type flip-flop 404 to activate the calibrationsequence. As discussed above, the calibration sequence can generallyinclude two phases, shown as the dashed boxes P1 to represent phase 1,and P2 to represent phase 2. Of course, the calibration sequence couldbe organized into other portions, ordering of portions/phases, or othersubsets of operation.

In the examples described herein, in the first phase at 906, a referencevoltage for a differential or sense amplifier (or other circuitry underconsideration) can be increased by an adjustment voltage. For example,adjustment voltage VADJ can be added to nominal reference level REF(see, e.g., reference level adjustor 306) in order to test one “side” orexpected output of the amplifier or circuit. At 908, a first result fromreading an amplified output of the amplifier can be stored. For example,latches 502-0/502-1 in FIG. 5 can be used to store this first phasecalibration result, in order to apply a predetermined mapping togenerate updated control signal voltages.

In the second phase at 910, a reference voltage for a differential orsense amplifier can be decreased by an adjustment voltage. For example,adjustment voltage VADJ can be subtracted from nominal reference levelREF (see, e.g., reference level adjustor 306) in order to test the otherside or expected output of the amplifier. At 912, a second result fromreading and amplified output of the amplifier can be stored. Forexample, latches 502-2/502-3 in FIG. 5 can be used to store this firstphase calibration result. At 914, the first and second phase results canbe used (e.g., via logic circuits corresponding to a predeterminedmapping) to set control gate voltages for dual-gate transistors in theamplifier (or other circuit under consideration), and the flow cancomplete at 916. In one example of predetermined mapping, as shown abovein Tables 1 and 2, the first and second phase results can be mapped tocontrol signals CGR and CGD.

The flow can also include repetitions of the sequence, such as formultiple memory cells or memory arrays, or multiple instances of anyappropriate circuitry under consideration, whereby suitable controlsignal settings can occur for each, or a subset of, the multiple circuitinstances. As will be discussed in more detail below, a memory arrayincluding a plurality of memory cells can be tested using a calibrationsequence as described herein, and this may be repeated for all cells inan array, for multiple arrays, and/or multiple circuit instances. Forexample, such calibration sequence(s) can occur as part of a power upsequence, or another initialization sequence, of a semiconductor device.As another example, such calibration sequence(s) can occur as part of atest/characterization sequence prior to sending a semiconductor deviceto a customer. As yet another example, such calibration sequence(s) canbe initiated by a customer as part of a field-based optimizationprocedure.

In particular embodiments, a semiconductor memory device can include amemory array with amplifiers that include dual-gate transistors, as wellas associated calibration circuitry. In one embodiment, a semiconductormemory device can include: (i) a memory array comprising a plurality ofdata amplifiers, wherein each of the data amplifiers comprises first andsecond dual-gate transistors; (ii) a plurality of register pairs coupledto the plurality of data amplifiers, wherein each of the register pairscomprises a first register configured to store a first control signalfor a control gate of the first dual-gate transistor, and a secondregister configured to store a second control signal for a control gateof the second dual-gate transistor; and (iii) a calibration controlcircuit configured to generate the first and second control signals fora selected of the plurality of data amplifiers.

Referring now to FIG. 10, shown is a schematic block diagram of anexample calibration control arrangement for a memory array, inaccordance with embodiments of the present invention. Example memoryarray and calibration control 1000 can include memory array 1002,registers 1004, multiplexer 1006, and offset calibration control 104.Memory array 1002 can include any type of memory cell (e.g., volatile,non-volatile, resistive, dynamic, etc.), and sense amplifiers 102 (e.g.,102-0, 102-1, 102-2, . . . 102-7). Shared data lines (not shown) canconnect between memory cells or other amplifiers and sense amplifiers102, and sense amplifiers 102 may be considered data or I/O amplifiers,whereby the data input to sense amplifiers 102 can be from any suitablememory configuration or other circuitry.

The calibration sequence as described above can be performed for one ormore of amplifiers 102. For example, address select signals ASEL[2:0]can be used to select one of sense amplifiers 102 for calibration, andthen the sequence can be formed for an adjacent of sense amplifiers 102,and so on. Alternatively, a certain sense amplifier can be selected forcalibration due to other test or characterization results, and in thiscase the calibration sequence as described herein can be a supplementalprocess to an underlying test/characterization process. In some cases,input offset can occur on one or some subset of the sense amplifiers,and this can be determined via other testing/characterization. As aresult, the affected sense amplifiers can be selected (e.g., viaASEL[2:0]) for calibration and adjustment of the control gates ondual-gate transistors of interest, in order to improve or otherwisemodify the performance of that particular sense amplifier(s). As anotherexample, the calibration sequence can be performed on one or some subsetof sense amplifiers 102 based on other test/characterization results,such as reduced margins for reading a given data state, and the causecan be a reason other than input offset. Thus, the calibration sequenceas described herein is amenable to a variety of test, characterization,and/or circuit aspect or performance modifications.

Thus, address select (e.g., column address select) signals can bereceived by registers 1004 and multiplexer 1006, and may be used toselect the appropriate sense amplifier 102 for a given calibrationsequence. Thus, each of data outs (e.g., DO-0, DO-1, DO-2, . . . DO-7)from sense amplifiers 102 can be provided to multiplexer 1006 forselection to a single data out provided to offset calibration control104. The result of the calibration sequence can then be provided fromoffset calibration control 104 to registers 1004. Registers 1004 canstore control signal CGR/CGD information for the appropriate senseamplifier. If no calibration is performed on a given sense amplifier, orif no adjustment is needed based on the results of the calibrationsequence, the control signals CGR/CGD corresponding to a given senseamplifier 102 can remain in their default state. In this way,calibration circuitry can be shared among a number of circuits (e.g.,sense amplifiers) under consideration for control gate modification.

Referring now to FIG. 11, shown is a schematic block diagram of anexample of register and multiplexer circuitry for calibration controlfor a memory array, in accordance with embodiments of the presentinvention. Example 1100 can include circuitry found in registers 1004and multiplexer 1006. Registers 1004 can include a pair of latches 1102to store the control signals CGR/CGD corresponding to each amplifier102, or other circuit under consideration. In some cases, the particularcircuit under consideration may have only one dual-gate transistor witha control gate to be modified as part of the calibration sequence. Inthese cases, instead of a pair of latches 1102, only a single latch maybe used corresponding to the given circuit under consideration.

As shown in the latch circuit 1102-D0 when the appropriate addresssignals (e.g., 000) and timing signals match via NOR-gate 1152,NAND-gate 1154, and inverter 1156, the transmission gate can open. Thus,when the output of inverter 1156 is high, NMOS transistor 1106-D0 can beturned on, and PMOS transistor 1104-D0 can also be turned on viainverter 1114-D0, to allow CGD to be captured in latch 1102-D0. Once theoutput of inverter 1156 goes low to turn off the transmission gate, thiscontrol signal can be held via inverters 1108-D0 and 1110-D0, and may bebuffered via inverter 1112-D0 such that control signal CGD-0 can beprovided to corresponding sense amplifier 102-0. In addition, latch1102-D0 can be reset low via NMOS transistor 1116-D0 when the addresssignals match via NOR-gate 1152 and calibration enable signal CEN isactive, as determined via NAND-gate 1148 and inverter 1150, in order toset the local control signal CGD-0 as low during the calibrationprocess. Alternatively, a pull-up transistor can be employed in place oftransistor 1116-D0 if the default state of the corresponding localcontrol gate signal is to be high.

Similarly, as shown in latch circuit 1102-R0 when the appropriateaddress signals (e.g., 000) and timing signals match via NOR-gate 1152,NAND-gate 1154, and inverter 1156, the transmission gate can open. Thus,when the output of inverter 1156 is high, NMOS transistor 1106-R0 canalso be turned on, and PMOS transistor 1104-R0 can also be turned on viainverter 1114-R0, to allow CGR to be captured in latch 1102-R0. Once theoutput of inverter 1156 goes low to turn off the transmission gate, thiscontrol signal can be held via inverters 1108-R0 and 1110-R0, and may bebuffered via inverter 1112-R0 such that control signal CGR-0 can beprovided to corresponding sense amplifier 102-0. In addition, latch1102-R0 can be reset low via NMOS transistor 1116-R0 when the addresssignals match via NOR-gate 1152 and calibration enable signal CEN isactive, as determined via NAND-gate 1148 and inverter 1150, in order toset the local control signal CGR-0 as low during the calibrationprocess.

Similar selections and controls can occur for latch pair 1102-D1 and1102-R1 that correspond to control signals CGD-1 and CGR-1,respectively, and which also correspond to sense amplifier 102-1. Thetransmission gates in latches 1102-D1 and 1102-R1 can be open when theappropriate address signals (e.g., 001) and timing signals match viainverter 1146, NOR-gate 1140, NAND-gate 1142, and inverter 1144. Inaddition, latches 1102-D1 and 1102-R1 can be reset low when the addresssignals match via inverter 1146 and NOR-gate 1140, and calibrationenable signal CEN is active, as determined via NAND-gate 1136 andinverter 1138, in order to set the local control signals CGD-1 and CGR-1as low during the calibration process.

Similar selections and controls can occur for the other latches inregisters 1004, including latch pair 1102-D7 and 1102-R7 that correspondto control signals CGD-7 and CGR-7, respectively, and which alsocorrespond to sense amplifier 102-7. The transmission gates in latches1102-D7 and 1102-R7 can be open when the appropriate address signals(e.g., 111) and timing signals match via NAND-gate 1134, inverter 1126,and NOR-gate 1128. In addition, latches 1102-D7 and 1102-R7 can be resetlow when the address signals match via NAND-gate 1134, and calibrationenable signal CEN is active, as determined via NOR-gate 1132 andinverter 1130, in order to set the local control signals CGD-7 and CGR-7as a low default state during the calibration process, as discussedabove.

The register update control signal UDCGSREG can be generated as aone-shot or pulse signal upon a falling edge of update control signalUDCGS. This pulse signal can be a duration substantially of delaycircuit 1120, an output of which can be inverted via inverter 1122, andinput to NOR-gate 1124. NOR-gate 1124 can thus provide a high goingpulse signal upon a high to low transition of update control signalUDCGS. In this way, the control signals as provided to registers 1004can be updated after the global CGR and CGD control signals have beenupdated via offset calibration control 104. Thus, the local controlsignals for sense amplifiers 102 can be updated after the global controlsignals coming from shared calibration circuit 104 have been updated.

Particular embodiments are suitable for a wide variety of circuits underconsideration for calibration (e.g., differential amplifiers, senseamplifiers, input receivers, etc.), and also to a wide variety of inputcombinations for such circuitry under consideration. As will bediscussed in the examples below, input receivers (e.g., to receive avalue from an external pin), including purely differential inputreceivers, low voltage swing terminated logic (LVSTL), etc., can also beaccommodated in certain embodiments. Of course, other circuitry,including circuits that may have only one dual-gate transistor with acontrol gate in order to modify circuit operation as a result of thecalibration sequence, can also be accommodated.

Referring now to FIG. 12, shown is a schematic block diagram of anexample amplifier and calibration control arrangement for an inputreceiver, in accordance with embodiments of the present invention. Inexample 1200, input receiver 1202 can receive data input (e.g., I/O dataor DQ) from an external connection to the chip. Offset calibrationcontrol 1204 can receive calibration enable command signal CENCMD andclock signal CLK, and DATAIN as output from input receiver 1202. Forexample, reference voltage level REF can be directly applied to inputreceiver 1202. Thus, additional adjustment setting signals may not beneeded in this case because reference level REF may be an input to thedevice that can also be adjusted through external control as part of thecalibration process. Offset calibration control 1204 can provide controlgate signals (CGR, CGD) and non-calibration sense amplifier enablesignal SENNCB can be input to NAND-gate 106 along with calibrationsequence sense amplifier enable signal SENCB, such that sense amplifierenable signal SEN can be output from NAND-gate 106.

This particular arrangement can be used to change characteristics ofinput receiver 1202 by way of control signal adjustment on one or morecontrol gates of dual-gate transistors in input receiver 1202.Calibration control 1204 can be employed to effectively change inputreceiver trip points, thus adapting input receiver 1202 to differentsignaling characteristics on data input DQ. Thus for example, thecalibration sequence as described herein can be applied to effectivelymodify the I/O interface of the device, even to adapt to differentsignaling characteristics or protocols, thereby allowing thesemiconductor device to be used in a variety of applications withouthaving different mask sets or other controls to adapt the input receivercircuitry in order to properly determine the data state of the inputsignal. Instead, dynamic calibration circuitry as described herein canbe used to appropriately modify circuit behavior of input receiver 1202.

Referring now to FIG. 13, shown is a schematic block diagram of anexample input receiver with dual-gate transistors, in accordance withembodiments of the present invention. Input receiver 1202 can includedual-gate (e.g., FinFET) transistors 1302 and 1304. Dual-gate transistor1302 can receive reference level REF at a signal gate, and controlsignal CGR at a control gate. Also, dual-gate transistor 1304 canreceive I/O data DQ at a signal gate, and control signal CGD at acontrol gate. NMOS transistors 1306 and 1308 can form the loadtransistor portion of the input receiver. Also, the input receiver canbe enabled via SEN provided to inverter 1312, with an output connectedto the gates of PMOS transistor 1310 and NMOS transistor 1314.

A ratioed inverter stage can include PMOS transistor 1316, and NMOStransistors 1318 and 1320. Inverter 1322 can then be utilized to providethe input receiver output, DATAIN. In the ratioed inverter stage, one ormore of these devices could alternatively or additionally be implementedas independently controlled dual-gate transistors whereby their controlgates can be modified by way of the calibration circuitry. This isanother way that input receiver 1202 trip points could be modified inorder to adjust the input receiver to different input signalcharacteristics. Particular embodiments may also support single endedinput receivers in much the same fashion. In such cases where a singleended or non-differential amplifier is to be adjusted, the phase 1 andphase 2 portions of the calibration sequence can be modified to includeonly a single phase, or to test different circuit aspects or expectedoutcomes in the predefined phases.

Referring now to FIG. 14, shown is a schematic block diagram of anexample calibration controller for an input receiver, in accordance withembodiments of the present invention. Offset calibration control 1204can include calibration timing control 302 and calibration controlcircuit 304. As discussed above, calibration timing control 302 cangenerate various timing signals utilized by other circuits in thecalibration sequence or process. Calibration timing control 302 canreceive calibration enable command signal CENCMD and clock signal CLK,and may generate calibration enable signal CEN, phase 1 enable latchcontrol signal ELP1, phase 2 enable latch control signal ELP2, updatecontrol gate signal pulse UDCGS, and calibration sequence senseamplifier enable signal SENCB.

Calibration control circuit 304 can receive calibration enable signalCEN, phase 1 enable latch control signal ELP1, phase 2 enable latchcontrol signal ELP2, update control gate signal pulse UDCGS, and DATAINfrom input receiver 1202, and may generate control signals CGR and CGDfor the control gates of transistors 1302 and 1304 in input receiver1202. In this case, reference level REF can be controlled (e.g.,externally) to be an increased or decreased voltage relative toreference level, in order to effectively test both sides of inputreceiver 1202. As discussed above, modifications to this examplecircuitry can be made in order to support a single phase and/or to testdifferent circuit aspects or expected outcomes, such as in single ended(as opposed to differential) signaling or amplification.

Referring now to FIG. 15, shown is a schematic block diagram of anexample amplifier and calibration control arrangement for an inputreceiver with differential inputs, in accordance with embodiments of thepresent invention. In example 1500, input receiver 1502 can receivedifferential input data (e.g., D+ and D−), such as from an external chipconnection. As discussed above, offset calibration control 1204 canreceive calibration enable command signal CENCMD and clock signal CLK,and DATAIN as output from input receiver 1502. In this particularexample, no reference level need be utilised, because the data is purelydifferential, and adjustments can be made based on these externalsignals. As such, additional adjustment setting signals may not beneeded in this case because the input data D+/D− can be adjusted throughexternal control as part of the calibration process.

Referring now to FIG. 16, shown is a schematic block diagram of anexample input receiver with dual-gate transistors and differentialinputs, in accordance with embodiments of the present invention. Similarto the example discussed above, input receiver 1502 can includedual-gate (e.g., FinFET) transistors 1302 and 1304. However, in thiscase the inputs may be purely differential, and thus the differentialinputs may be sensed with respect to each other, as opposed one beingsensed relative to a reference voltage level. Dual-gate transistor 1302can receive differential input D− at a signal gate, and control signalCGR at a control gate. Also, dual-gate transistor 1304 can receivedifferential input D+ at a signal gate, and control signal CGD at acontrol gate. NMOS transistors 1306 and 1308 can form the loadtransistor portion of the input receiver. Also, the input receiver canbe enabled via SEN provided to inverter 1312, with an output connectedto the gates of PMOS transistor 1310 and NMOS transistor 1314. A ratioat inverter stage can include PMOS transistor 1316, and NMOS transistors1318 and 1320. Inverter 1322 can then be utilised to provide the inputreceiver output, DATAIN.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilise theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

What is claimed is:
 1. A semiconductor device, comprising: a) a firsttransmission gate coupled between a reference voltage and an adjustedreference voltage, and being off during a calibration sequence, whereinthe calibration sequence comprises first and second phases; b) adigital-to-analog converter (DAC) configured to provide an adjustmentvoltage to be added to or subtracted from the reference voltage toproduce the adjusted reference voltage; c) second and third transmissiongates coupled between the reference voltage and the adjusted referencevoltage, and being enabled to provide the adjusted reference voltageduring the first phase and disabled during the second phase; and d)fourth and fifth transmission gates coupled between the referencevoltage and the adjusted reference voltage, and being disabled duringthe first phase and enabled to provide the adjusted reference voltageduring the second phase, wherein the adjustment voltage is receivedbetween the intervening node between the second and third transmissiongates and the intervening node between the fourth and fifth transmissiongates.
 2. The semiconductor device of claim 1, wherein the adjustedreference voltage is equal to about the reference voltage plus theadjustment voltage during the first phase.
 3. The semiconductor deviceof claim 1, wherein the adjusted reference voltage is equal to about thereference voltage minus the adjustment voltage during the second phase.4. The semiconductor device of claim 1, wherein the adjusted referencevoltage is equal to about the reference voltage when the calibrationsequence is complete.
 5. The semiconductor device of claim 1, whereinthe adjusted reference voltage is coupled to a signal gate of adual-gate transistor, and the calibration sequence is used to set acontrol gate of the dual-gate transistor.
 6. The semiconductor device ofclaim 1, wherein: a) the adjusted reference voltage is coupled to asignal gate of a first dual-gate transistor, and a control gate of thefirst dual-gate transistor is coupled to a first control signal; and b)the first dual-gate transistor is coupled to a second dual-gatetransistor via sources thereof, the second dual-gate transistor having asignal gate coupled to a data input, and a control gate coupled to asecond control signal.
 7. The semiconductor device of claim 1, whereineach of the first and second dual-gate transistors comprises a FinFET.8. The semiconductor device of claim 1, wherein the first transmissiongate is on when the calibration sequence has completed.
 9. Thesemiconductor device of claim 1, wherein the DAC is disabled when thecalibration sequence has completed.
 10. The semiconductor device ofclaim 1, further comprising a plurality of latches coupled to the DAC,and configured to receive a plurality of adjustment setting signals. 11.The semiconductor device of claim 10, wherein the adjustment voltage isbased on the plurality of adjustment setting signals.
 12. Thesemiconductor device of claim 11, wherein the adjustment setting signalsare latched in the plurality of latches in response to activation of thecalibration sequence.